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#ifndef hmap_cpp
#define hmap_cpp
#include "hmap.h"
using namespace std;
bool is_prime( int n );
int next_prime( int n );
// Construct the hash table.
template <class obj_type, class key_type>
hmap<obj_type, key_type>::hmap( double mop )
: i_max_occupied_percentage(mop), array( next_prime( 101 ) )
{
lookups = 0;
make_empty( );
}
// Insert item x into the hash table. If the item is
// already present, do nothing
template <class obj_type, class key_type>
void hmap<obj_type, key_type>::add_elem( const obj_type &x, const key_type &k )
{
// Insert x as active
int i_current_pos = find_pos( k );
if( is_active( i_current_pos ) )
return;
array[ i_current_pos ] = hash_entry( x, k, ACTIVE );
if( ++occupied > array.size( ) * i_max_occupied_percentage )
rehash( );
}
// Expand the hash table.
template <class obj_type, class key_type>
void hmap<obj_type, key_type>::rehash( )
{
vector<hash_entry> old_array = array;
// Create new double-sized, empty table
array.resize( next_prime( 2 * old_array.size( ) ) );
for( int j = 0; j < array.size( ); j++ )
array[ j ].info = EMPTY;
// Copy table over
make_empty( );
for( int i = 0; i < old_array.size( ); i++ )
if( old_array[ i ].info == ACTIVE )
add_elem( old_array[ i ].element, old_array[ i ].key );
}
// Hash function, can only handle strings.
// If you want to hash other objects you will have to
// create a hash table for them
template <class obj_type, class key_type>
unsigned int hmap<obj_type, key_type>::hash( const string & key ) const
{
unsigned int hash_value = 0;
// cout << key << "%";
for( size_t i = 0; i < key.size(); i++ )
hash_value = ( hash_value << 5 ) ^ key[ i ] ^ hash_value;
return hash_value;
}
// Method that performs quadratic probing resolution.
// Return the position where the search for x terminates.
template <class obj_type, class key_type>
int hmap<obj_type, key_type>::find_pos( const key_type &k )
{
int i_collision_num = 0;
int i_current_pos = hash( k ) % array.size( );
lookups++;
while( array[ i_current_pos ].info != EMPTY &&
array[ i_current_pos ].key != k )
{
// cout << array[ i_current_pos ].element << "!=" << x << endl;
lookups++;
i_current_pos += 2 * ++i_collision_num - 1; // Compute ith probe
if( i_current_pos >= array.size( ) )
i_current_pos -= array.size( );
}
// cout << i_current_pos << " ";
return i_current_pos;
}
// Remove item x from the hash table.
template <class obj_type, class key_type>
void hmap<obj_type, key_type>::del_elem( const key_type & k )
{
int i_current_pos = find_pos( k );
if( is_active( i_current_pos ) )
array[ i_current_pos ].info = DELETED;
}
// Find item x in the hash table.
// Return a pointer to the matching item or 0 if not found
template <class obj_type, class key_type>
obj_type hmap<obj_type, key_type>::get_elem( const key_type &k )
{
int i_current_pos = find_pos( k );
if( is_active( i_current_pos ) )
return array[ i_current_pos ].element;
else
return 0;
}
// Make the hash table logically empty.
template <class obj_type, class key_type>
void hmap<obj_type, key_type>::make_empty( )
{
occupied = 0;
for( int i = 0; i < array.size( ); i++ )
array[ i ].info = EMPTY;
}
// Return true if i_current_pos exists and is active.
template <class obj_type, class key_type>
bool hmap<obj_type, key_type>::is_active( int i_current_pos ) const
{
return array[ i_current_pos ].info == ACTIVE;
}
// Internal method to test if a positive number is prime.
// Not an efficient algorithm.
template <class obj_type, class key_type>
bool hmap<obj_type, key_type>::is_prime( int n ) const
{
if( n == 2 || n == 3 )
return true;
else if( n == 1 || n % 2 == 0 )
return false;
for( int i = 3; i * i <= n; i += 2 )
if( n % i == 0 )
return false;
return true;
}
// Internal method to return a prime number at least as large as n.
// Assumes n > 0.
template <class obj_type, class key_type>
int hmap<obj_type, key_type>::next_prime( int n ) const
{
if( n % 2 == 0 )
n++;
for( ; !is_prime( n ); n += 2 )
;
return n;
}
template<class obj_type, class key_type>
void
hmap<obj_type, key_type>::run_func( void (*func)(obj_type) )
{
for( int i = 0; i < array.size( ); i++ )
if ( array[i].info == ACTIVE )
( *func ) ( array[i].element );
}
template<class obj_type, class key_type>
void
hmap<obj_type, key_type>::run_func( void (*func)(obj_type, void*), void* v_arg )
{
for( int i = 0; i < array.size( ); i++ )
if ( array[i].info == ACTIVE )
( *func ) ( array[i].element, v_arg );
}
template<class obj_type, class key_type>
vector<key_type>*
hmap<obj_type, key_type>::get_key_vector()
{
vector<key_type>* p_vec = new vector<key_type>;
for( int i = 0; i < array.size( ); i++ )
if ( array[i].info == ACTIVE )
p_vec->push_back( array[i].key );
return p_vec;
}
#endif
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